[packaging] add some additional metadata bits to setup.cfg

omits licensing information for now pending discussion on #91

setup.cfg

 [metadata]
 name = dnadna
+description = Deep Neural Architecture for DNA
+long_description = file: README.md
+long_description_content_type = text/markdown
+author = The DNADNA Developers
+maintainer_email = embray@lri.fr
+url = https://gitlab.com/mlgenetics/dnadna
+classifiers =
+    Development Status :: 3 - Alpha
+    Environment :: Console
+    Environment :: GPU :: NVIDIA CUDA
+    Intended Audience :: Science/Research
+    Programming Language :: Python :: 3.7
+    Topic :: Scientific/Engineering :: Bio-Informatics
+
 
 [options]
 python_requires = >= 3.6